1. Field of the Invention
This invention relates to method and apparatus for preparing crimped fibrous structures and more particularly to means for crimping textile fibrous materials such as synthetic filaments, yarn, tow, staple fibers and the like.
2. Description of the Prior Art
In the apparatus conventionally used to crimp textile strands to increase their bulkiness, a tow of continuous filaments is forced against a mass of tow within a chamber, and emerges in crimped form from the chamber when the pressure on the mass exceeds a certain limit. The number of crimps produced by such apparatus per inch of the filaments as well as the shrinkage, or crimp contraction level produced in the filaments is too low for economical processing of the filaments into high quality knitting yarns, fabrics, high stretch yarns and the like. Moreover, pressure variances on the mass can clog the chamber or alter the residence time of filaments therewithin, thereby damaging the filaments and reducing their tensile strengths and/or dyeing uniformity. It has been proposed to regulate the residence time of filaments in the chamber by providing the latter with a continuously moving surface. Such apparatus improves uniformity of crimp and reduces streaks in fabrics produced from the filaments, but does not increase appreciably the number of crimps per inch and/or the shrinkage level of the filaments.